U.S. Pat. No. 4,621,976, Integrally Cast Vane and Shroud Stator With Damper granted to the co-inventors of this patent application, on Nov. 11, 1986 and assigned to United Technologies Corporation, the assignees of this patent application, discloses and claims a damping scheme utilized in the identical application as the present invention and is incorporated herein by reference. As noted from this patent, supra, an annular shaped channel is formed into the shroud of the cast stator and receives an annularly shaped (C-shaped in cross section) dampening element. The damping device is in essence, a spring that has one leg bearing against one side wall of the C-shaped annular channel and the other leg biased against the opposing parallel wall of the C-shaped channel. This effectively preloads the inner shroud of the vane and dissipates the energy occasioned by the vibratory motion of the component elements of the stator. The vanes are all mutually attached at both ends as part of the stator casting. The damper acts on this common surface and only inhibits that motion which is coupled onto this surface from the individual vanes. This invention constitutes an improvement over the one disclosed in the referenced patent.
This invention contemplates eliminating the C-shaped channel and restructuring the cast stator so as to effectively free one end of the cast stator and bias that end by a spring like damping element. In the preferred embodiment the inner shroud carries a depending annular member defining a radially inwardly extending support structure. One or more annularly shaped dampening elements are supported to this member having a free cantilevered end biasing the inner shroud. The inner shroud is slotted between adjacent vanes and the slot extends through the annular depending member allowing the inner shroud and the individually attached vanes to have freedom of movement, limited, however by the stiffness of the material used. The land seal element of the typical labyrinth seal is also supported to the depending member, so that damping of this element is also attained by this construction.